Re: [Xen-devel] Poor network performance between DomU with multiqueue support

["Zhangleiqiang (Trump)" <zhangleiqiang@xxxxxxxxxx>]

> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxx
> [mailto:xen-devel-bounces@xxxxxxxxxxxxx] On Behalf Of David Vrabel
> Sent: Tuesday, December 02, 2014 6:57 PM
> To: zhangleiqiang; xen-devel@xxxxxxxxxxxxx
> Subject: Re: [Xen-devel] Poor network performance between DomU with
> multiqueue support
> 
> On 02/12/14 08:30, zhangleiqiang wrote:
> > Hi, all
> >     I am testing the performance of xen netfront-netback driver that
> > with multi-queues support. The throughput from domU to remote dom0 is
> > 9.2Gb/s, but the throughput from domU to remote domU is only 3.6Gb/s,
> > I think the bottleneck is the throughput from dom0 to local domU.
> > However, we have done some testing and found the throughput from dom0
> > to local domU is 5.8Gb/s.
> >     And if we send packets from one DomU to other 3 DomUs on different
> > host simultaneously, the sum of throughout can reach 9Gbps. It seems
> > like the bottleneck is the receiver?
> >     After some analysis, I found that even the max_queue of
> > netfront/back is set to 4, there are some strange results as follows:
> >     1. In domU, only one rx queue deal with softirq
> >     2. In dom0, only two netback queues process are scheduled, other
> > two process aren't scheduled.
> 
> Multiqueue only has benefits if you have multiple flows since the
> source/destination addresses are hashed to a queue number.  This probably
> explains why only some of the queues are being used in your test.

The hash method you mentioned is used for selection of netback process or 
netfront rx queue? 
Indeed, there are 4 netback processes running in Dom0, because there are only 
one DomU running in Dom0 and so four netback processes are running in Dom0 (the 
max_queue param of netback kernel module is set to 4). 
The phenomenon is that only 2 of these four netback process were running with 
about 70% cpu usage, and another two use little CPU.

> David
> 
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